More than a century after citizen armies became an international norm, nearly two dozen states actively recruit foreigners into their militaries. Why do these states skirt the strong citizen-soldier norm and continue to welcome foreigners? To explain this practice, we first identify two puzzles associated with foreign recruitment. The first is practical: foreign recruits pose loyalty, logistical, and organizational challenges that domestic soldiers do not. The second is normative: noncitizen soldiers lie in a normative gray zone, permitted under the letter of international law but in tension with the spirit of international norms against mercenary armies. Next, we survey foreign military recruitment programs around the world and sort them into three broad types of programs, each with its own primary motivation: importing expertise, importing labor, and bolstering international bonds. We explain these categories and explore three exemplary cases in depth: Australia, Bahrain, and Israel. Our findings suggest that foreign recruitment can affect a state’s military operations by allowing militaries to rapidly develop advanced capabilities, by reducing the political risk associated with the use of force, and by expanding a state’s influence among former colonial and diaspora populations.